1. Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device that prevents color change due to a viewing angle direction.
2. Discussion of the Related Art
In recent years, since an organic light emitting display device has been developed using poly-phenylene vinylene (PPV), which is a conjugate polymer, studies on organic materials such as a conjugate polymer having good conductivity have been active. Studies for applying such an organic material to a thin-film transistor, a sensor, a laser, a photoelectric element, and the like have been continuously carried out, and among them studies on organic light emitting display devices have been most active.
In case of light emitting display devices made of phosphor-based inorganic materials, an operating voltage above 200 VAC is required and the display device is fabricated by a vacuum deposition process. Such displays are difficult to fabricate with a large-size display, have poor blue light emission characteristics, and have high fabrication cost. However, organic light emitting display devices made of organic materials have been highly regarded as the next generation display devices due to advantages, such as the facilitation of a large-sized screen, the convenience of a fabrication process, and particularly easy implementation of blue light emission, as well as allowing the development of a flexible light emitting display device, and the like.
Similar to liquid crystal display devices, active matrix organic light emitting display devices having an active driving element for each pixel have been considered for implementation as a flat panel display. Such an organic light emitting display device may include an anode, a cathode and an organic light emitting unit therebetween, and the organic light emitting unit emits white color. In the case of emitting white color as described above, the organic light emitting unit is deposited with luminescent materials for emitting red, green and blue, and thus, the combined light thereof becomes white color.
However, in the case of an organic light emitting display device for emitting white color, the locations of luminescent materials (or emission layers) for emitting red light, green light and blue light are different, thereby causing difficulty in coinciding cavity peak phases for each wavelength. As a result, variation between a cavity peak and a photoluminescence peak may occur, thereby causing a problem of reducing image quality.